The Maillard reaction takes place when food components like reducing sugars and amino acids react together. This reaction occurs in most foods on heating. Maillard reaction chemistry can affect desirable flavors and color of a wide range of foods and beverages including malts and beers, bread, snacks. coffee, heated fruit and vegetable products, breakfast cereals, and meat.
One problem with efforts to enhance toast flavor in oat groats or their derivatives such as cut groats, bumped groats, flour, dough, flakes, etc., via Maillard reactions is the coincidental oxidation of lipids naturally contained in significant quantities in oat grain. The oxidized lipids can cause undesired off-flavor and rancidity.
Lipid oxidation can be initiated by the same thermal energy employed to activate and drive Maillard reactions to produce reaction products imparting favorable flavors. Once initiated, the lipid oxidation becomes auto catalytic and cannot be controlled easily, if at all. Complicating matters oat groats contain natural enzymes which must be deactivated to stabilize the groat (or its derivatives) composition from degradation by the enzymes.
Conventionally, groats are tempered with steam two deactivate the enzymes, at least in part. A typical steam tempering process ranges from 12 to 15 minutes where the temperature of the groat reaches 210-220.degree. F. The tempered groats are then processed through a kiln where they are subjected to more heat, typically ranging up to 240.degree. F. During this kilning process the groats remain in a relatively high humidity (steam) atmosphere.
This process is generally successful at deactivating enzymes, avoiding rancidity, and producing a "cooked" flavor. However, the process is time and energy intensive and produces only a minimal toast flavor. Conventional kiln equipment also takes up substantial space and poses a relatively large capital expenditure.
Also an imposing problem, is the obstructive morphology of the oat grain (or groat) itself. It appears that it is not well understood how to optimize Maillard reaction chemistry within the oat groat cellular structure itself, that is, in situ.
Accordingly, in an attempt to provide a successful enhancement of toast flavor to a final oat food product, others have conventionally shifted their focus from the difficult problem posed by the groat's natural morphology to its more accessible derivative forms, down-stream of the groat pre-processing . For example, U.S. Pat. No. 4,963,373 issued to Fan et.al discloses a toasting step involving oat flour dough, after a flaking process for a ready to cat ("RTE") cereal product. With respect to lipid oxidation during attempts to enhance toast flavor, even these other methods rely on the addition of antioxidants such as BHA and BHT, before or after toasting to retard oxidation of the lipids.
None of these approaches provide a solution for dealing with enhancement of toast flavor in the gross cellular structure of either whole groats or split, cut, cracked, bumped, or flattened groats. Such forms of the oat groat are desired in consumer cooking as main the main constituent to make for example, an oatmeal porridge or an oatmeal cookie. They are also used in popular pre-prepared consumer products such as cereal bars, snack bars, textural coatings, etc., where the oats either provide an adjunct enhancement to flavor and texture of the product or serve as a main constituent of the product, such as
However, recently others have attempted improvements in adding toast flavor during the initial processing (or pre-processing) of oat groats. In particular, U.S. Pat. No. 5,523,109, issued to Hellweg et.al. discloses a method where "whole oat groats are steamed for greater times, dry toasted for extended times" in an attempt to provide a toasted oat flour after milling of the groat. Hellweg el. al. states that "minimal peroxidase activity and a ratio of the HPLC syringic acid peak to ferulic acid peak, of about .gtoreq.2.5 which ratio is characteristic of a toasted flavor attribute." However, neither Syringic/Furulic acids, nor phenolic acids in general, are believed by the present inventors to accurately reflect the formation of desired Maillard reaction products. Hence, the degree of success of this process is in doubt, or at least not demonstrated. Further, the Heliweg et. al. process suffers two further drawbacks.
First, it employs steps which are energy and time intensive, in particular. "steaming for greater times" and dry toasted for "extended times." Kilning is also included between the steaming and dry roasting step. This is not only a disadvantage in cost and manufacturing efficiency, it also exposes the groat to extensive thermal energy, risking the initiation of autocatalytic oxidation of the lipids.
Second, the Hellweg et. al. process has as a (coal, to partially gelatinize or precook the groat. (See Hellweg et. al. reference to Farinograph measurements). This precooking and or partial gelatinization is not necessarily desirable when the groat is to be used in its integral or near-integral form, for example: as a cut groat, or rolled oat for consumer cooking into a porridge, or as either a whole groat or rolled groat as might be used in a granola or snack/cereal bar as an enhancing texturizer or as a main constituent.
In addressing these problems, the present inventors examined the unique attributes and constraints associated with whole oat groats and the Maillard reactions thought to be of interest for providing a toast flavor. Most notable is the constraint on reaction kinetics presented by the three dimensional morphology presented by the biological and cellular make up of a groat.
Also considered were the Maillard reactions themselves in terms of optimizing production of favorable products by providing conditions favorable to desired reaction paths occurring in the three basic phases of the Maillard reactions. In particular, the initial reactions ("Phase I Maillard reactions") are condensations of amino acids with simple sugars, which each lose a molecule of water to form N-substituted aldosylamines. These are unstable and undergo Amadori rearrangement to form 1-amino-1-deoxy-2-ketoses, also known as "ketosamines."
These ketosamines can then undergo complex subsequent reaction paths toward Phase III products, generally characterized as either: (1) dehydration; (2) fission; or, (3) polymerization, reactions ("Phase II Maillard reactions").
The first Phase II path is simply for the ketosamines to further dehydrate (i.e. loss of two water molecules) into reductones & dehydro reductones. Reductones and dehydro reductones, in their reduced state, are powerful antioxidants.
The second Phase II path produces short chain hydrolyctic fission products, such as, diacetyl acetol, pyruvaldehyde etc.
In a third path from Phase II products to Phase III products. polymerization occurs to yield furfural and melanoids.
It is a goal of the present invention to at least enhance the second path of Phase II, so as to ultimately produce favorable nitrogen heterocycles in particular, pyrazines and thiazoles (Phase III Maillard products).
Due to the morphology of the oat grain (or groat) it was proposed that the simple sugars, were constrained to an appreciable degree from physical molecular movement in within the groat; hence, were limited in their opportunity to come into contact with amino acids for reaction. To address this, it was proposed to increase the mobility of these simple sugars (i.e. mono, di, tri, and tetra, saccharides) by solubilizing them within the groat. Solubilization, it was believed, might be accomplished in significant degree by adding sufficient moisture to the groat. The amount of moisture necessary for this solubilization was then examined experimentally, as discussed below, although it was initially believed that between 1.5 to 2.0 times the normal amount of moisture contained in the groat may suffice, i.e. 21-30%.
It was also proposed that because dehydration reactions are a desired Phase II path, after mobilization of the simple sugars and/or amino acids, physical dehydration of this added moisture may help drive Phase II reaction equilibrium.